From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 25E9BC4727D for ; Tue, 6 Oct 2020 14:18:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C575520782 for ; Tue, 6 Oct 2020 14:18:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726164AbgJFOSW (ORCPT ); Tue, 6 Oct 2020 10:18:22 -0400 Received: from netrider.rowland.org ([192.131.102.5]:33521 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1725947AbgJFOSV (ORCPT ); Tue, 6 Oct 2020 10:18:21 -0400 Received: (qmail 417731 invoked by uid 1000); 6 Oct 2020 10:18:20 -0400 Date: Tue, 6 Oct 2020 10:18:20 -0400 From: Alan Stern To: Matthias Kaehlcke Cc: Doug Anderson , Rob Herring , Greg Kroah-Hartman , Frank Rowand , "linux-kernel@vger.kernel.org" , Linux USB List , Bastien Nocera , Stephen Boyd , Ravi Chandra Sadineni , Krzysztof Kozlowski , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , Peter Chen Subject: Re: [PATCH v4 1/2] dt-bindings: usb: Add binding for discrete onboard USB hubs Message-ID: <20201006141820.GA416765@rowland.harvard.edu> References: <20200929220912.GF1621304@google.com> <20200930013229.GB194665@rowland.harvard.edu> <20200930124915.GA1826870@google.com> <20201006004510.GD4135817@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201006004510.GD4135817@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 05, 2020 at 05:45:10PM -0700, Matthias Kaehlcke wrote: > I did some prototyping, it seems a binding like this would work for > case a) or b): > > &usb_1_dwc3 { > hub_2_0: hub@1 { > compatible = "usbbda,5411"; > reg = <1>; > }; > > hub_3_0: hub@2 { > compatible = "usbbda,411"; > reg = <2>; > vdd-supply = <&pp3300_hub>; > companion-hubs = <&hub_2_0>; > }; > }; > > It still requires specifying both hubs (which reflects the actual wiring). > Supporting something like "reg = <1 2>" seems more complex due to the need to > obtain the hub USB device at runtime (a DT node makes that trivial), possibly > this could be solved by adding new APIs. > > In terms of implementation would I envision to keep a platform driver. This > would keep the hubby parts out of xhci-plat (except for populating the platform > devices), support systems with cascaded hubs and provide a device for the sysfs > attribute. What will you do if a system has more than one of these power-regulated hubs? That is, how will the user know which platform device handles the power control for a particular hub (and vice versa)? You'd probably have to create a pair of symlinks going back and forth in the sysfs directories. Wouldn't it be easier to put the power-control attribute directly in the hub's sysfs directory (or .../power subdirectory)? Alan Stern